This invention relates to liner pipes for use in the repair of pipes, and preferably for trenchless reconstruction of underground pipes such as sewer lines.
Deterioration of underground pipes due to aging is a major problem. Aging of underground pipes results in corrosion, loose joints, cracks, holes and missing sections in pipes. Excavation and replacement of deteriorated underground pipes such as sewer lines is extremely costly, time consuming and disruptive to traffic, utilities and other activities in the area surrounding the excavation site.
Prior art liner pipes have been developed for "trenchless" reconstruction of underground pipes, completely eliminating the need for excavation in most cases. Liner pipes are typically inserted into a damaged section of pipe from above ground at an end of the pipe to be repaired. The damaged pipe into which the liner pipe is inserted is typically referred to as the "host" pipe. After insertion, the liner pipe is molded to conform to the inner size and shape of the host pipe, thus effectively providing it with a new lining.
During manufacturing of a typical prior art liner pipe, the cross-sectional size and shape of the liner pipe is substantially reduced by deformation. This typically involves folding the liner pipe along its longitudinal axis, giving it a U-shaped cross-section and a substantially reduced cross-sectional area and size. This reduced cross-sectional shape and size allows the liner pipe to be smoothly inserted into the host pipe.
After insertion into the host pipe, the liner pipe is unfolded to increase its cross-sectional size and shape and conform it to the inner cross-sectional shape and size of the host pipe.
Typically, the prior art liner pipe is rigid when inserted and the entire liner pipe must be softened by heating before it can be unfolded. In one prior art method, heat is applied by passing pressurized steam through the liner pipe, thus heating the pipe from the inside only. As a result, more heat is applied to the inner surface of the liner pipe than the outer surface, and the inner surface becomes softer than the outer surface. This uneven heating causes uneven expansion of the liner pipe, and can result in gaps being left between the outside of the liner pipe and the inner surface of the host pipe.
one prior art system has been developed which simultaneously heats both the inside and outside of the liner pipe. This produces even heating, resulting in even expansion and a tight fit of the liner pipe inside the host pipe.
This prior art system utilizes a thin, flexible plastic sleeve which is first inserted into the host pipe. A conventional, prior art folded liner pipe is inserted into the sleeve so that the sleeve completely surrounds the liner pipe. Pressurized steam is passed through the sleeve, evenly heating both the inside and outside of the liner pipe.
The even heating of the liner pipe achieved by this system results in even expansion and a high quality installation, with the liner pipe fitting tightly inside the host pipe.
However, the sleeve cannot be recovered and reused after installation of the liner pipe. The sleeve remains inside the host pipe between the host pipe and the installed liner pipe. The use of a new sleeve for each installation increases the material cost of the repair process. Further, the extra step of inserting the sleeve into the host pipe substantially increases the labour and the time required for the installation.
The prior art liner pipes and methods have disadvantages, some of which are discussed above, which relate to ease and expense of installation.